Different Types of HAZOP

Different Types of HAZOP Appendix II - 1

A P P E N D I X I 1

Different Types of HAZOP A. Parametric Deviation Based HAZOP

Parametric Deviation Based HAZOP relies on establishing sets of commonly applied deviations by establishing typical parameters/properties/operations and assigning Guide Words (such as High, Low, No, Part of, Other than, As well as, etc.).

The resultant deviations effectively form a "library of deviations" which can be repetitively used, depending on the equipment type being HAZOPed.

It is the most widely used form of HAZOP in the world today

Advantage of Parametric Deviation Based HAZOP

It has the advantage of giving reasonably consistent results and is simple to use. It also adds a certain degree of quality assurance.

Disadvantage of Parametric Deviation Based HAZOP

It has the disadvantage that certain interactions and special case deviations may be overlooked. In addition, more deviations than are really required may also be processed, thus consuming excessive time and effort.

Furthermore the basis for using such established deviations is experience as opposed to a basic methodology based on logic1 reasoning.

An ultra conservative approach would be to use a very extensive list of deviations, say around 20 (or even more), for every node reviewed. However, such an approach is very time consuming.

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Different Types of HAZOP Appendix 11 - 2

This could lead to frustration, boredom and lack of co~iviction, by team members, that any specific deviation is particularly relevant; this can compromise quality.

The key to efficient HAZOPs is:

1. Making node sufficiently large to minimize repetition 2. Using correct deviations (not too many, not too few) 3. Control of HAZOP sessions (See Chapter 19)

The following table, Table 11-1, shows typical Deviations for Various Items of Equipment.

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Parametric Deviation based Methodology

Table 11-1: Examples of Equipment Types and Assigned HAZOP Deviations

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DEVIATION

High Suction Pressure

High Pressure

High Discharge Pressure

High Temperature

High Discharge Temperature High Flow

High Bonoms Level

High Concentration of Impurities Low Pressure

Low Suction Pressure

Low Flow, Low1 No Flow Low Temperature

Low Bottoms Level

Low Tray Level

Reversel Misdirected Flow Column Flooding

Contaminants Enter Equipment Leakage

Rupture

Cavitation

Maintenance Hazards

Startup1 Shutdown Hazards Loss of Performance

CENTRIFUGAL COMPRESSOR

X

X

X

X

X x x

CENTRIFUGAL PUMP

x

x x X

COLUMN

x

X X X

x X X

X

x x

X X

FURNACE HEATER

X

x

X

X

X X

X

X x x

HEAT EXCHANGER

X

x

- -

X

X

X (Tube 8 Shell) X (Tube 8 Shell)

X

LINE

X

X

X

X

X

X

X x x

2003 by CRC Prcss LLC

Different Types of HAZOP Appendix I1 - 4

B. "Creative Identification of Deviations & Disturbances" Methodology for Performing HAZOPs

Ref "A Manual of Hazard & Operability Studies - The Creative Identification of Deviations and Disturbances" by R. Ellis Knowlton, published by Chemetics International Ltd., 1992

Example:

Consider a kettle, operating on a batch basis, into which are fed several liquids - X and Y - for mixing and emulsification. Consider that X is being pumped from a supply drum to the kettle via a feed line.

The process intention can be described in the following words: "Transfer X from the supply drum to the kettle via supply pump and feed line." The design intention is analyzed in terms of 5 specific components: Node, Material handled, Activity undertaken, Source, and Destination. See the following table.

Advantages

Node Material Activity Source Destination

Thorough Good for batch type operations

Supply Pump and Feed Line X Transfer Supply Drum Kettle

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Disadvantages

Not all deviations may be valid or could be hard to interpret.

May be cryptic and hard to audit unless very well documented. Can be hard to apply to continuous operations.

The deviations are obtained by applying Guide Words to Material, Activity, Source, and Destination, as follows:

Table 11-2: Deviations derived by applying Guide Words to Material, Activity, Source, and Destination

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Material Activity

Source

Destination 7

MORE

More X Transfer more

More from supply drum

More to kettle

LESS

Less X Transfer less

Less from supply drum Less to kettle

REVERSE

Reverse X Reverse transfer

Reverse from supply drum Reverse to

kettle

AS WELL AS

As well as X As well as

transfer As well as from

supply drum As well as to

kettle

PART OF

Part of X Part of transfer

Part of from supply drum

Part of a kettle

OTHER THAN

Other than X Other than

transfer Other than from

supply drum Other than to

kettle



C. Procedural HAZOP

Batch processes are often used to produce various kinds of materials in the chemical

industry. Continuous operations are also operated in batch modes, e.g. during startup, shutdown, maintenance, etc.

In such cases the HAZOP can be performed by sequentially analyzing the operating

procedures of the particular batch process.

The operating instructions of the batch process are divided and simplified and rewritten, if necessary, so that each instruction represents the design intention.

For e.g., one instruction might be "Fully open valve V-101 to transfer 4500 kg of reactant X to the reactor R-201." This can be broken into more elemental actions; "Fully open V-

101" and "Transfer 4500 kg of X into R-201". Each can then be combined with Guide Words to establish deviations, as follows.

Not / Fully open V- 10 1 As well as / Fully open V- 10 1 More / Transfer 4500 kg of X into R-201 Less / Transfer 4500 kg of X into R-201, and so on.



Procedural HAZOP Example

Procedure Description

The start-up operations of the light ends column C-101 is used to illustrate the hazard and operability technique used in batch processes. The following steps illustrate the procedures followed during the startup of the column. (See Figure 11-1 for reference)

1. Put cooling water on light ends condenser EX- 102 to condense light ends flashing from feed.

2. Open bypass around PV-106 to allow non-condensibles to pass to flare without pressure build-up in light ends stripper, C-101.

3. Set FRC-101 on feed supply to minimum setting (after opening up battery limit valve on feed from feed drum V- 10 1).

4. When level in base of column reaches normal liquid level on LIC-110 crack open manual by pass around TV- 126.

5. Observe level in reflux drum V-102 on LIC-107 and close manual bypass around PV-106 ensuring that setpoint of PIC-106 is set for normal design when low level is reached on LIC- 107.

6. Start reflux pump P- 10 1 and ensure total reflux with FRC- 1 16 set for design flow. 7. Increase steam on reboiler to design flow by setting TRC-126. 8. When medium high level is almost reached in column bottoms, LIC-119, start

bottoms pump P- 102. With LV- 1 19 fully closed maintain minimum flow conditions on P- 102.

9. Stop feed to column, maintain reflux but do not export distillate or bottoms. Keep reboiler running and maintain check on overheads composition.

10. When overheads material is fully up to specification introduce more feed at reduced flowrate and export distillate and bottoms to maintain equilibrium.

1 I. Increase feed flow to design flowrate over duration of shift.



Figure 11-1: P&ID of Light Ends Process

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Procedural Step Evaluation In the above example, each of the startup procedures was considered to be a node and the deviations associated with each of these nodes were evaluated. The procedure is illustrated using the first procedure. Startup Procedure: Put cooling water on light ends condenser EX-102 to condense light ends flashing fiom feed.

Assigned Node: Cooling water on light ends condenser EX- 102

Deviations:

No cooling water on light ends condenser EX-102 SoonerILater cooling water on light ends condenser EX- 102 More cooling water to EX-102 Less cooling water to EX-102

Reverse cooling water to EX-102 Other than cooling water to EX-102 As well as cooling water to EX-102

Deviation: No Cooling water on light ends condenser EX- 102 Cause: Frozen pipeline in winter Consequence: Can't startup Safeguards: %" Bypass line which is electrically traced Recommendations: Ensure that there is a low point drain and a high point vent

Similar evaluation is conducted on each of the above nodes. The above procedural step methodology can be conducted to evaluate batch operations, operating procedures, operating manual instructions etc.


Different Types of HAZOP Appendix I I - 10

Table 11-3: Example of Procedural HAZOP Worksheet for Light Ends

10:33:09 AM 512210 1 Node: 1. Cooling water on light ends condenser EX-102. Drawing: Type: Procedural Step

drain and a high point vent.

(1.3. More cooling water to EX-102 T l l c o n s e q u e n c e s ImSafegllardsmkIIRR(I~ecolnmendations

1 1.4. Less cooling water to EX- 102

1 1.5. Reverse cooling water to EX- 102 m l c o n s e q u e n c e s l l S a f e g l l a r d s ~ ~ ~ ~ ~ R e c o m m e n d a t i o n s l [ ~ e s ~ o n s i b l e I I . N o c a u s e s n n n - 7 1


Different Types of HAZOP Appendix II - 11

lternatively provide extended



r2.5. Reverse Bleed non condensibles to flare via bypass around PV-106 1 ~esponsible

12.6. As well as Bleed non condensibles to flare via bypass around PV- 106

T l l ~ o n s e q u e n c e s I m S a f e g u a r d s m E l l R e c o m l n e n d a t i o n s fl~esponsible p i Z K i q ~ l n n n ~ ~ 1

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Node: 3. Minimum feed supply fiom V- I0 I to the column C- 10 1 Type: Procedural Step

Drawing: Fig A 2.1

3.1. No Minimum feed supply from V- I 0No l to the column C-101

13.2. More Minimum feed supply from V-101 to the column C-101 ' ~ f l ~ [ ~ [ i l e s p o n s i b l e ,

1. Operator 1.1. Rapid start- 1. I. None 1 3 3 10. Update operating instructions Operations sets setpoint up and possible to manually crack open steam on on FRC- I0 I loss of control. reboiler at start prior to feed

1 3 3

~ ~ ~ ~ ~ ~ ~ z ; ~ i ~ r ~ ; t h e o p e r a t i n g vaporization in the column during start-up earl hase.

13.3. Less Minimum feed supply from V- 10 l to the colu~nn C- 10 1 v l l ~ o n s e ~ u e n c e s l l S a f e g L l a r d s ~ ~ ~ / l ~ e c o m m e n d a t i o n s

1

1 1 . Start-up at 25% feed rate to be Operations ri 2003 by CRC Prcss LLC


Advantages of Procedural HAZOP

include checking of level of liquid in upstream feed from V- 10 1.

1. Good for HAZOPing batch operations.

2. Good for HAZOPing Operating Manuals, including Start-up, Shutdown etc.

Disadvantages of Procedural HAZOP

drum V-101

1. Limited for HAZOPing continuous operations.

2. Can be time consuming.

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3 -

3 13. Ensure that there is a vortex breaker in the upstream vessel V- 10 1 bottoms.

Eng. Dept.



D. Knowledge Based HAZOP

This methodology typically is sometimes applied in place of the Guide Word Methodology. Some assumptions are:

Extensive design standards and procedures are in place. HAZOP team has experience with similar designs. Process being HAZOPed is well established.

Basis is to use detailed Knowledge Based Checklists and brainstorm process for possible I

deficiencies.

Table 11-4: Example of Knowledge Based Checklist for Centrifugal Compressor

TYPE = COMPRESSOR (CENTRIFUGAL) COMPRESSOR SUCTION

QUESTION = Suction side overpressured from backflow/ leakage of recycle valve on compressor shutdown?

QUESTION = Interstage equipment overpressured from backflow/,leakage of recycle valve on compressor shutdown?

QUESTION = Suction side overpressured from backflow or recycle leakage with parallel compressors?

QUESTION = Interstage equipment overpressured from backflow or recycle leakage with parallel compressor?

QUESTION = Does suction side have permanent strainer with local pressure indication downstream?

QUESTION = Does suction side have low-pressure alarm and, possibly, trip at low pressure?

QUESTION = Do suction/ interstage knockout drums have high liquid level alarms and trips at high high liquid level?

QUESTION = Will the compressor be shut down at low suction pressure?

QUESTION = Are air compressors intakes protected against contaminants (flammables, carbon monoxide, etc. ) ?



Table 11-5: Applicability of Different Types of HAZOP

Note: More ticks are better -

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PARAMETRIC DEVIATION BASED HAZOP

GUIDE WORD (ELLIS KNOWLTON METHOD) PROCEDURAL STEP

KNOWLEDGE BASED HAZOP

EXISTING PROCESS

J J J (If Continuous)

JJJ (If Batch)

JJJ (If Batch)

JJJ

OPERATING MANUAL

STARTUP & SHUTDOWN

J

1/44

JJJ

J

BATCH

J

JJJ

1/44

J

CONTINUOUS

1/44

d

J

JJJ

NEW PROCESS

JJJ (If Continuous)

JJJ (If Batch)

J (If Batch)

J



SUGGESTED READING (Note: URLs current at date of publication) "Apply the HAZOP Method to Batch Operations" by R.L.Collins, Chemical Engineering Progress, April 1995, pages 48 to 5 1 www.che.com/ "Guidelines for Hazard Evaluation Procedures" by AIChE, CCPS, 2"d edition, 1992 plus "Guidelines for Hazard Evaluation Procedures" by AIChE, CCPS, 1st edition, 1985 u~w~~~.aichc.org/p~L~cat/s~ac1tl.as~~?Act~~C~&Catcgor~~=~Scct4&M in=20 "A Manual of Hazard & Operability Studies - The Creative Identification of Deviations and Disturbances", published by Chemetics International, 1992 www.kvaerner.con.~~companics/co1n~~~1niesdt-.tail.as~:'id=796 "DOE Handbook - Chemical Process Hazards Analysis", (Website) http:!~tis.el~.doe.~ov/techstdsistandi~rd/11dbl1 100/htlbk I lOO.~?dt'


Guidelines for Process Hazards Analysis, Hazards Identification & Risk AnalysisTable of ContentsAPPENDIX II: Different Types of HAZOPA. Parametric Deviation Based HAZOPB. "Creative Identification of Deviations & Disturbances" Methodology for Performing HAZOPsC. Procedural HAZOPD. Knowledge Based HAZOP

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Different Types of HAZOP